Chuck



E. FINSEN June 2, 1931.

CHUCK Filed 2 Sheets-Sheet l IN VENTOR ggz/zrzd 22726670 %zls ATTORNE E. FINSEN 1,808,347

CHUCK I June 2, 1931.

Filed June 3, 1929 2 Sheets-Sheet 2 INVENTOR his ATTORNEY Patented June 2, 1931 UNITED STATES PATENT oFFlcsf nrvmn FINSEN, or noonns'rnn, NEW YORK, ASSIGNOR r0 GLEASON. -WOR-KS, or

ROCHESTER, NEW YORK, A CORPORATION OF N'Ew YoRK v CHUCK Application filed June 3,

l The present invention relates to hydraulic control devices and particularly to hydraulically operated mechanism such as may be used in conjunction with a chucking attachment for releasing the chuck. In a more particular aspect, the invention relates to chucking attachments such as are employed on machines for cutting tapered gears, namely, bevel and hypoid gears.

The present invention is an improvement over my prior invention disclosed in application No. 308,537 filed September 26, 1928. Its purpose, in general, is to provide a mechanism more positive in operation, one less liable to get out of order and one which will more readily adapt itself to varying conditions which occur in use. I

Other objects of the invention will be apparent hereinafter from the specification and from the recital of the appended claims.

In the drawings:

Figure 1 is a fragmentary plan view of a bevel gear generating machine which is provided with a chucking mechanism incorpo rating in its construction the features of the present invention, part of the machine and work arbor being shown in section;

Figure 2 is a layout on an enlarged scale of the mechanismof the present invention; and

Figure 3 is a fragmentary view of the plunger pump constituting part of this mechanism, parts being shown in section.

The present invention has been illustrated in connection with a chuck for a bevel gear generating machine. The draw-bar of the chuck is constantly urged into chucking position by a coil spring which acts against one end of a piston that is connected to the draw-bar and is housed in a cylinder which is mounted on the work spindle of the machine. The draw-bar is moved to released position against the resistance of the spring by application of fluid pressure to the opposite end of the piston through actuation of a plunger pump which is secured to the frame of the machine at a point convenient to the operator and connected to the cylinder by flexible piping. The pump, p ping and cylinder act as a closed'hydraulic system, that is, when the plunger is depressed in the pump, the oil or'other liquid used is forced out of the. pump into the piping and pressure is applied to the piston to compress the spring and move the draw-bar to released position and when the pressure is released, the spring returns the draw-barto chucking position forcingthe oil out of the cylinder and back through thepiping into the pump chamber. I

The system is connected by means of a valve-closed duct with areservoir on the machine. WVhen the plunger of the pump is depressed, the valve is closed. The valve is connected'by a stem with the plunger and means is provided for; raising the plunger automatically, thus opening the valve as soon as the plunger is raised. The purpose of this construction is two-fold, first, to permit escape of the oil from the system should there be an excess of oil in the system which 7 might prevent the spring from functioning properly to chuck'and secondly, to permit oil to be-drawn into the system should-the supply of oil in the system'require replenishing due to leakage.

The present mechanism is constructed so that should any air become: entrapped in the system and thereby prevent proper operation of the hydraulic release, it may be pumped out of the pump and out of the system. Means is provided, also, for collecting the oil drawn up by the plunger asit rises .to inoperative position and returning the same to the main reservoir of the machine.

With some types of gears, it is impossible with the limited-withdrawal movement provided on the work head or tool headof a bevel gear cutting machine to get the work off and on the work spindle conveniently. With the present invention, however, means is provided for drawing the cylinder, and with it the draw-bar bodily backward so that after the work has been released, the draw-bar can be drawn out of the bore of the work piece to permit the work piece to drop off of the work spindle while by a reversal of the motion a new blank can be chucked. This improvement very greatly increases the capacity of a gear cutting machine on which'it is installed.

Reference may now be had to the accompanying drawings for a more complete understanding of the present invention. The machine shown is of the type described in U. S. Patent No. 1,660,502 issued to James E. Gleason et alPFebruary 28, 1928. It includes a bed or-frame on which is slidably mounted a tool head indicated generally at 11 which carries a pair of reciprocating tools, one of 'whichistobe-se'enat 12 in-the drawings. The frame 10 is provided at one-end with an upright 13 which is formed with ways 14 which receive the rails 15 of the cradle 16 which is oscillatable on the upright. The upper face of the cradle is provided with arcuate slots 17 and the work head 18 which is angularly adjustable on the upper face of the cradle is held in any adjustedposit-ion by means of.

T-hol-ts 19 which engage in these slots.

J ournaled in the'worfk head 18 is asleeve :20 to-which is connected a ;gear segment 21 -which engages a segment 22 that is secured toa relatively fixed part of the machine. The sleeve20 is connected to the work spindle 24 during cutting by the index mechanism which is enclosed in the housing indicated at 25.

The generating .motion is imparted to the work spindle by oscillation of the cradle 16 which in turn causes the segment 21 to roll on the segment 22. Fora more complete description of this mechanism and its operation, reference-maybe had to the above mentioned patent. It is to be understood, however that the presentinvention is-not restricte'dto use with .a machine'of the type herein illustrated but is capable of very general application. Reference has been had to a machine on which thepresent mechanism may be used, simply tomakethe use, operation and construction of the present .invention more readily understandable.

. One form of apparatus for-clampingthe gear blank G te be cut to the work spindle .is shown in Figurel. :Fhis includes the draw-bar 30, the horseshoe washer 31 and the arbor-32. The gear-blank G and then the horseshoe washer 3-1 are slipped on to the draw-bar. When the draw-bar is drawn backward in the spindle, the gear is forced against'theiar hor'andthe arbor in turn forced @int'o t'he taper bore of the spindle while the horseshoe washerserves to hold the gear on the draw-bar.

The invention is not confined 'touse with a clamping mechanism'such as ust described but maybe employed in connection j with any *o'thersuitableclamping mechanism as, forinstance, acolle'tchuck.

. 24l -by -means :of the nut '37 which threads into i one endof'thecylinder and engages thehead "of a "sleeve 38 that is mounted on the drawrod and in a suitable recess formed in the end of the work spindle 24.

The draw rod 30 is constantly urged toward and forced into chucking position by a coil spring 40 which surrounds the draw rod 30 and abuts at one end against the head of the sleeve 38 and at the other end against one side of the piston 35. The piston is preferably recessed, as shown, to receive the spring 30 as the compass of the chucking mechanism is thereby reduced to a minimum. To release the work-piece G it is necessary to compress the coil spring and take off the horseshoe washer 31. The spring 40 is compressed by application of fluid pressure to theopposite side of'the piston 35, through actuation of aplunger pump 42.

Secured within a hole bored in the end of the cylinder 36, as by means of'a pin 43 is .a stud 44. This stud is drilled centrally at 45 for a portion of its length and diametrically at 46 to provide a duct for conductingoil "or a similar fluid into the cylinder. The. stud 44 is threaded at its outer end to receive the nut 48. The nut 48 and the washer 49 which is,

with. a circular groove 52 that communicates.

with the duct 46 formed-in thestud 44. The sleeve 51 is also drilled to provide" a duct 53 that communicates with the groove 52.

A suitable packing is provided, as'indicated at 55 to prevent leakage ofoil around the stud and sleeve and a leather cup or washer 56 is secured to the piston 35 by the washer 57 and nut 58 toprevent leakage along the piston.

The pump 42 is connected to. the sleeve-51 by the-coupling 60, the flexible hose 61, and the coupling 62 which includes a manually operable valve 63. The'pump .42 is pivotally mounted in a bracket 65 which is secured in any convenient position on the frame of the machine so that the pump will be conveniently located for operation by the operator of the machine. The pump is-detachably secured to this bracket by means of a catch 66 which is pivotally secured to the bracket 65 and engages the trunnion pin 67 of the pump.

The pump plunger is shown at 70. It is operated by a hand lever 71 that is pivotally connected to the bracket 65by the stud 72 and is pivotally connected to the plunger 7 0 by the pin 73. 74 designates a rod and 75 a weight which is secured-t0 the rod at its outer end. The rod 7 4, is secured to the lever 71 at a position to normally move thelever 71 and plunger 7 O to raisedposition.

The plunger is hollowed out to receive the stem 76 of the valve 77. This valve 77 is adapted to engage a seat formed in the nipple 78 below the point where the coupling 62 threads into the ;nipple. The nipple is threaded into the pump chamber 42 proper.

The valve 77 controls the duct 7 9. which may be connected with the oil reservoir or one of the oil pumps of the machine or may communicate by means of a tube 81 with a reservoir such as shown at 80in Figure 2 which is threaded onto the end of the nipple 78.

The valve stem 7 6 is threaded at its upper end to receive the nut 82 and the lock-nut 83.

The system comprising the pump 42, nipple 78, coupling 62, hose 61, coupling 60, duct 53, groove 52, ducts 46 and 45 and the cylinder 36 is adapted to be kept as full of oil as is possible when the draw-bar is in .clamping position and the piston is in its rearward position in the cylinder 36 under actuation of the spring 40 and when the plunger 7 0 is in raised position. When the plunger is depressed by operating the lever 71, the column of oil in the pump 42 first closes the valve 7 7 and is then forced through the piping 61 into the cylinder 36 to compress the spring 40,

'move the draw-bar 3O forward in the work Lil-5 .chucking attachment would not be flexible spindle 24 and release the work-piece. As soon as the operator releases the lever 71, as

-" after removing the completed gear and chucking a new blank, the spring forces the piston 35 rearwardly again to move the draw-bar 30 again to chucking position. This operation is accelerated by the action of'the weight 7 5 which lifts the lever arm 71 and the plunger 70 automatically, thus affording room in the pump 42 for the column of oil which is forced out of the cylinder 36 by the return of the piston 35 to chucking position. As the plunger 7 O rises, the bushing 84 which is threaded into the lower end of the plunger engages the nut 82 lifting the valve 7 6 and opening the system through the duct 79. The nut 82 is adjusted so that the bushing 84 will engage it and open the valve 77 just before the rod 74 strikes the stop ledge 86 on the bracket 65.

It is impossible with present manufacturing methods to eliminate entirely variation in gear blank dimensions. Some blanks will always be slightly larger than others. If

the system were to remain closed at all times,

thus containing a constant volume of oil, the

enough to take careof the variation in gear sizes which normally occur in practise. The chucking attachment might be adjusted to take a gear of a particular size. If a gear a few thousandths of an inch smaller than this size occurred in the lot, to chuck it properly, the draw-rod 30 and piston 35 would have to be forced back farther than for the standard sized gear. But if the volume of oil in the system were constant, this would resist the movement of the piston" 35 back farther than the predetermined distance so that the gear would not be properly seated on the arbor and the arbor in the spindle.

. With the system opened, however, automati really when the lever 71 is released, should'a ume of oilwillhe forced out plunger; handle valve 63 is closed and the set screw 92is turned to releasethe ball 91 from its small gear occur in the lot, the chuckin at-' tachment will function just as well as or a gear of the standard size for the extra volof the system through the duct 79.

occurs, a greater volume of oil is required in the system to release the chuck. Oilleakage is bound to occur and if the mechanism is to work properly at all times, this must be re- If the reservoir is used, it can be refilled from time totime through the oil-cup 88 and the volume of oil in the reservoir can be observed at any time throughfthe sightglass 89.

With a mechanism functioning as de scribed, it is necessary to exclude air entirely from the system. If there were any air in the system it would simply compress on the down stroke of the plunger 70 and the chuck would not be released. Through a very simple and ingenious arrangement, any air which might become entrapped in the pump can be readily pumped therefrom, and a plug or valve is provided at some other convenient point in the system to permit forcing air out of the rest of the system."

The plunger 70 of the pump is drilled at its upper end, above the chamber for the valve stem 7 6, to provide a duct' 90 (Fig. 3 which is normally closed by the ball-valve 91 which is heldclamped inits seat by the setscrew 92 that threads into the side of. the To empty the pump of air, the

seat. Then the plunger 70 is moved down in the pump chamber by operating the lever 71. With the lever held down the set-screw 92 is retightened. Then the plunger is raised and the operations repeated until oil begins der is on the upper side of the cylinder. The

plug 94 is then unthreaded a turn or two.

The spring 40 is then compressed as far as possible by actuating the pump andfwhile the pump lever is held down, the hand valve 63 is closed. The lever/T1 is then released sucking more oil into the pump.- The hand 70 When a gear a few thousandths oversize valve is then opened and the additional oil in the pump forced into the system. This procedure is continued until oil begins to seep around the threads of the plug 94. When the oil seeps out :along the plug, the

' system will die free ofair and the plug again whereby the oil is wiped ofl' of the plunger on each down stroke :and returned to the sump or reservoir in the machine. The cap 95 of the pump is recessednasshown at 96. Thus as the plunger 70 is moved'downward- 1y, the'oil is wiped off of the plunger intothis pocket or recess :96. It flows thence into a duct 97 drilled into thecap'95and into :a tube 98 inserted in this duct 97. The tube 98 extends beyond "the side of the pump and over a pocket 99 formed in the bracket 65. The oil dripping from the tube 98 falls into this pocket 99 and is conducted through itheduct 100 into the sump of the machine. The tube 98 is always over the pocket 99 regardless of the pivotal movement of the pump.

The cylinder 36 can be ad]usted on the nut '37 to permit of taking care of a wide range of gears. .In the machine shown, the tool head 11 "is moved backward to permit of taking ofi a finished gear or chucking a new blank. In other types of machines, the work head is moved away from the tools for this same purpose. Where fiat gears are being cut, for instance, it frequently occurs that the withdrawal movement provided on the tool head or work .head of the machine is not suflicient to carry the workaway from the tools far enough to permit chucking or unchucking a gear. The present improvement incorporates as one of its features an arrangement whereby, once thegearhasbeen released, the draw-rod 30 can be drawn 1nwardly to clear the 'boreof thegear-and permit the gearfto dropoff the spindle. This 1s illustrated in Figure .1.

Secured to-thesleeve'51 at a po nt approximately 90 away from the point at which-the coupling is threaded into 'the'sleeve 1s :a rod 102 which is also supported from the work head by the-arms '103and 104111 which the rod is slidable. Secured to the-rod as by a set-screw (not shown) is a collar 105 to which is pivoted a link 106 which is pivoted to a bell-crank lever 107, the long'arm of which is formed with an operative handle 108. The bell'crank lever 107 is pivoted on a T-bolt 110 which is adjustable with the -work head in the slot 17 of the face 'of the cradle.

It will be seen that through the slidable i connectionbetween-thestud 38 (Fig. 2) and" thework spindle 24, that when'the lever arm 108 isturned to the left from 'the position shown in Figure .1, the :rod 102 will be moved rearwardly to draw the cylinder 36 and through the spring connection between the cylinder .and the piston 35 to draw the mar 30 rearwardly in the spindle 24. A collar .111 can be adjusted along the rod 102 and held by a set-screw to limit the movement of the rod 102'as desired.

The rod 102 holds the sleeve 51 against movement during the roll of the work spindle so that the flexible hose 61 is not twisted back and forth. To further :protect the hose against wear, bell-shaped guards lrla-nd 115 (Fig. 2) are provided where-the .hose connects, respectively, to the sleeve 51 and the coupling 62. A sleeve 116 which is belled :at both ends is secured to theframeofithe *machine to support the hose at an intermediate point.

To take a gear off of the chuck, :the operator'grasps the lever'71-to depress the plunger 70, thus forcing oil into the cylinder '36 and compressing the spring -40 and moving the draw-bar 3O forward :in the spindle. The

then be slipped off of-the draw-bar and a new' blank positioned thereon. If the range of movement of the tool head is not sufficient to enable the gear to be taken 0E and clear the tool, the operator swings the lever 107 to withdraw the draw-bar into the spindle and let the gear drop off.

In chucking a new'blank, the spring 40 is held compressed, the operator positions the blank onthe draw-bar, which will have been returned to position by movement of the handle 108 if it had been previously withdrawn, and the horseshoe washer 31 is slipped onto the draw-bar. The lever 71 is then released and the spring 40 functions automatically to clamp the gear blank to the spindle.

Y Vhile the invention has been described in connection with a particular embodiment and in connection with a particular use'for that embodiment, it will 'beunderstood that it is capableof further modification and use and that this application isintended to cover any variations, uses, or adaptations of the invention,'following, in general, the principlesof the invention and including such departures from the present disclosure as come within known or customary practise in the art to V piston movable therein and means for moving said plston in one directlon in said cyl inder, of a pump and piping connecting the pump with the opposite end of the piston, said pump, piping and cylinder forming a closed; hydraulic system such that when the pump forcing the liquid from said cylinder back into the pump chamber, and means for automatically connecting said system during the last named movement with a source of liquid supply to allow liquid to fiow in either di-' rection between the system and the source-of supply depending on the amount, oliliquid in the system.- 7 v 2. The combination with a cylinder, a piston movable therein and spring means for constantly urging the piston in one direction in the cylinder, of a pump and piping connecting the pump with the opposite end of the piston, said pump, piping and cylinder forming a closed hydraulic system such that when the pump is actuated, a column of liquid is forced from the pump chamber into the cylinder to move the piston inthe direction opposite to that first mentioned, and'when the pump is released, the spring means moves the piston in the first named direction in the cylinder forcing theliquid from the cylinder back into the pump chamber, and means for automatically connecting saidsystem during the last named movement with a source of liquid supply to allow liquid to flow in either direction between the system and the source of supply depending upon the amount of liquid in the system.

3. The combination with a cylinder, a pise ton movable therein, andmeans constantly urging the piston in one direction in the cylinder, of a plunger pump, piping connecting the pump with the cylinder at the opposite-end of the piston, a reservoir connected with the pump, a valve governing said connection adapted tobe closed when the plung er is depressedinthe pumpto forma closedhydraulic system between the pump and cylinder such that in the further depression of the pump hydraulic pressure is applied to the piston'to moveit against resistance of the first named means, means for automatically raising the plunger'in the pump when released, and meansfor automatically opening said valve on said last named movement.

4. The combination with a cylinder, apiston movable therein, andmeans constantly urging the v piston in one direction in the cylinder, of a plunger pump, piping connect ing the pump with the cylinder at the opposite end of the piston, a reservoirconnected with the pump, a valve controlling said connection adapted to be closed when the plunger is depressed in the pump to form a closed hydraulic system between the pump and cylinder such that on further depression of the plunger a hydraulic pressure is applied to the piston to move it against the resistance of said first named means, said valve having a stem slidable in said plunger, interengaging said valve when the plunger israised, and means for automatically raising said plunger when released. I

5. The combination with a cylinder, a piston reciprocable in saidcylinder and means constantly urgingsaid piston in one dime tion in said cylinder, of a plunger pump, piping connecting the pump with the cylin der atthe opposite end of the piston, a A

bracket on which the pump is pivotally mounted, a lever for operating the plunger pivoted on said bracket and pivotallyconnected to the plunger, means for urging said lever constantly in one direction tomove the plunger to raised position, a reservoir con-. nected with the pump, a valve controlling said connection adapted to be closed on depression of the plunger to form a closed sys-f tern between the pump and cylinder whereby on 'further depression of the plunger. hy' draulicv pressure is-applied to the .pistonto move it against the resistance of the .first named means, said valve having a stem slid- .able in said plunger, and meansfor coning means on the plunger and stem for ,opennecting the valve to the plunger so that when i the plunger israised, the valveis opened.

6. The combination with a spindle, a draw rod reciprocable in said spindle, a cylinder, a piston movable in the cylinder, and means for movingthepiston in the cylinder inops posite directions to move the draw rod'to and from chucking position, of means for moving the cylinder and with it the piston anad w rodbodily relative to the'spindle.

7. In a tapered gear cutting machine," a tool, a support, a work head angularly ad-Q justable on the support'to bring the root surface of the blank intotangency with the cutting planeof the tool, a work spindle journaled inthe head, a draw-rod for'clamping theiwork to the work spindle, a cylinder mounted on the head, a piston movable in the cylinder and connected tothe draw rod, meansfor moving the piston in opposite directions in the" cylinder for operating the draw rod, and means mounted on the support and adjustable angularly thereon with said head for moving the cylinder bodily relative to the spindle. r w

8. In a tapered gear cutting machine, a tool, a support formed with an arcuate T-slot on its upper face, a work head adjustable angularly on said support to bring the root surface of the blank'into tangency with the cutting plane of the tool, means adapted to the work to the work spindle, a cylindermounted on the head, a piston movable in the cylinder and; connected to the draw rod,

means for moving the piston in oppositedi' '5 rectio'ns in the cylinder for operating the draw-rod, a bolt secured in. the slot of the support and adjustable therein, a rod connected to the cylinder, and a" bell-crank lever pivotally mountedo'n the bolt for actuating said rod to move the cylinder bodily relative to a spring housed in the cylinder for urging the, draw rod constantly to clamping posi tiion', means for moving the piston in the 0pposite direction, and means mounted on the support and 7 adjustable angularly thereon with thehead'for moving the cylinder'bodily' relative; to the spindle.

7 1,01 The combination with a cylinder, a piston' 1moyabl'e V therein and means constantly urg ng the pistonin one directionin the cylinder, of. a plunger pump', piping adapted to connect'theipiston to the pump, a manually operable valve for shutting off said connection, a reservoir connected to the pump, a

second valve controlling said connection adapted to.be closed ondepression of the plunger in the pump and automatically p ned; when the plunger is raised, and a third valvehoused in theplunger at a point eX'ter'na'lof the pump, and means for keeping said third .valve closed duringthe normal operation of the pump, said means being releasable t'o perm it opening of the third valveiso that when the hand operated valve is. closed, the plunger may be operated to pump air out of the pump chamber.

IL The combination with a cylinder, a piston movable therein' and means constantly ur in'g the piston in one direction in the cylindenloi'means for applying fluid pressure to the opposite end of the piston for'forcing. the piston in the opposite direction comprising a plunger pump, and piping adapted to connectthe piston to the pump, and a manually operable valve, a reservoir connected to the pump, a second valve controllingsaid connect'ion adapted to be closed on depression of the plunger in the pump and automatically opened whenfthe plunger is raised, a ballvalve housed in the plunger, a screw for keeping said ball valve closedidnring the normal operation of the pump and adapted to be released when the hand valve is closed to permi't the plunger to be; operated to force the air out: of the pump chamber.

in In combination with a m chine having plunger, meansf external of the pump chamber for wiping oil from the plun er, a duct extending beyond the" periphery oi the pump chamber for conducting the wiped oil to one side of the chamber, and a ductinsaid bracket,

beneath the first named duct for catching the oil dripping from the first ductv and returning the same to thereservoir inthe; machine. V d

13;, The combination with a spindle; ofachucking attachment therefor comprising adraw rod reciprocable in the spindle, a cyl-- inder mounted on the spindle, a pistonsecure'd'to the draw rod and recipro'ca'ble in the" cylinder, means for moving the pist'on in one direction of the cylinder, a plunger-pump, pipi-ngconnec'ting' the pump t'oth'e cylinder at the opposite end of the piston, said cylinder, piping and pump constituting-in: operation,

a closed hydraul ib system whereby when the plunger is depressed irr the pump the piston isi'moved in the cylinder, a valve communi=- eating with the system adapted to be closed on depression at the pump plunger and means connecting; the valve with the plunger. for positively opening the valvewhen the plunger is-ra-ised in the pump; 14; The combination with a spindle, of a chucking attachment therefor comprising a draw rod' reeiprocable in the spindle, a cylinder" mounted on the spindle',' a piston secured to the draw rod and reciprocablf in the cylinder, means constantly urging the piston in one direction in the cylinder, a plunger pump,- piping connecting the pump to the cylinder at the opposite end of the piston-, said cylinder',;piping'and pumpcon'stituting,{inoperation,- a closed hydraul'ic system whereby when the plunger is depressed in the pumpthe piston is moved in the cylinder, a val vecommunica ti ng' with the system adapte'dtobe closed on depression ofthe pump and means, c'onnecting-the valve with the plunger for positively opening theval've when: the plunger is raisedinthe 'pump." 4

15.- The combination with-a spindle, of'a chucking attachment therefor; comprising a draw rod re'eiproe'ablethe spindle, a cyl indeimounted on the spindle, a piston secured to the draw rod and reeiprocable in the cylinder; meansconstantly urging the piston one direction inthecylinder, a plunger pump, piping connecting the pump with the cylinder at one-end of the-piston, said cylin der', piping and pnmp constituting operation a closed hydraulicsystem whereby when the plunger is depressedin the pump the piston 'ismoved in the cylinder against the. resistance' ofthe firstnained means, a valve communicating with the system adapted to be closed on depression of the pump, means connecting the valve with the plunger for opening the valve when the plunger is raised in the pump, and means for positively raising the plunger when released.

16. The combination with a spindle, of a chucking attachment therefor comprising a draw rod reciprocable in the spindle, a cylinder mounted on the spindle, a piston secured to the draw rod and reciprocable in the cylinder, means constantly urging the piston in one direction in the cylinder, a plunger pump, piping connecting the pump to the cylinder at the opposite end of the piston, said cylinder, piping and pump constituting, in operation, a closed hydraulic system whereby when the plunger is depressed in the pump the piston is moved in the cylinder against the resistance of the first named means, a reservoir connected with the pump, a valve controlling said connection adapted to be closed on depression of the plunger, means connecting the valve with the plunger for opening the valve when the plunger is raised in the pump, and means for positively raising the plunger when released.

17. In a machine for cutting tapered gears, a tool, a work head adjustable angularly to move the root surface of the blank into tangency with the cutting plane of the tool, a work spindle journaled in the work head, chucking mechanism therefor comprising a draw rod reciprocable in the spindle, a cylinder mounted on the spindle, a piston secured to the draw rod and reciprocable in the cylinder, means for moving the piston in one direction in the cylinder, a plunger pump, piping connecting the pump to the cylinder at the opposite end of the piston, said cylinder, piping and pump constituting, in operation, a closed hydraulic system whereby when the plunger is depressed in the pump the piston is moved in the cylinder, a valve communicating with the system adapted to be closed on depression of the plunger and means connecting the valve with the plunger for positively opening the valve when the plunger is raised in the pump and means for moving the cylinder bodily relative to the spindle.

18. The combination with a cylinder, a

piston movable therein, spring means operative on one end of said piston to constantly urge the same in one direction, a plungerpump, piping connecting the pump to the cylinder at the opposite end of the piston, said pump, piping and cylinder comprising a substantially closed hydraulic system containing a substantially constant volume of liquid whereby when the plunger is depressed in the pump chamber, the liquid is forced into the cylinder to move the piston against the resistance of the spring and when the plunger is moved outwardly of the pump 

